In 4/2he, what does the number 4 indicate?
the atomic number
the ion
the atomic mass number
the charge

The number 4 in the 4/2He indicates the atomic mass number of helium.

Option 3

Explanation:

The elements present in periodic table generally represented as . Here X will be the element in the periodic table, A is the atomic mass number of the element X and Z is the atomic number of the element X.

So, the number 4 is the atomic mass number of He and He-4 is the stable isotope of helium which can also be termed as alpha particle.

               Mass number = number of protons + neutrons count.

Thus the number 4 denotes the Helium's atomic mass number.

a electronegativity decreases beacuse the size of nucleus is bigger.